Filter screen tracking mechanism

ABSTRACT

A tracking means for maintaining a flexible endless belt filter media in proper alignment on its rollers. One of the rollers includes a center section of constant diameter, approximately the width of the limp portion of the belt, and a pair of end sections which are formed with a crown portion, the center of which is slightly greater than the diameter at each end of each end section. A flat, relatively narrow edging of relatively rigid material is fastened to both edges of the belt. Each edging tracks and aligns itself on one of the roller crowns. By locating the crowns at a slightly wider spacing than the spacing of the belt edgings the belt is kept laterally taut.

United States Patent [191 Shaffer 1451 Apr. 30, 1974 [75] lnventor:

52 05.0. ..210/401,74/241 [51] Int. Cl B0111 33/14 [58] Field of 210/400, 401, 216, 393;

[56] References Cited UNITED STATES PATENTS 6/1967 Sigely etal. 198/202 12/1931 Creedon et a1. 198/202 Primary Examiner-Charles Hart 571 ABSTRACT A tracking means for maintaining a flexible endless belt filter media in proper alignment on its rollers. One of the rollers includes a center section of constant diameter, approximately the width of the limp portion of the belt, and a pair of'end sections which are formed with a crown portion, the center of which is slightly greater than the diameter at each end of each end section. A flat, relatively narrow edging of relatively rigid material is fastened to both edges of the belt. Each edging tracks and aligns itself on one of the roller crowns. By locating the crowns at a slightly wider spacing than the spacing of the belt edgings the belt is kept laterally taut.

FILTER SCREEN TRACKING MECHANISM BACKGROUND AND SUMMARY OF THE INVENTION This invention relates to improvements in apparatus for tracking and maintaining the alignment of endless belts and more particularly to a tracking means for maintaining a flexible endless belt filter media, which does not yield to conventional belt tracking means, in proper alignment on its rollers.

Filtering apparatus frequently include the use of an endless belt filter medium, which usually takes the form of a filter cloth or a flexible plastic screen supported for rotation about two or more spaced apart rollers. It is known to track more rigid types of endless belts by forming a crown portion between the ends of one of the rollers. However, filter screens and other flexible belts become limp and ignore'the crown portion on the roller and tend to either run off the ends of the roller or run towards the crown portion from both edges and pile upon itself. Much work has been done, and many patents have issued disclosing various means to solve this problem. One such meansutilizes two edge gripping devices, a unit on either side of the belt, to grip a beaded edging and pull on the beltvto maintain alignment. Other known methods mechanically shift the belt back into correct alignment after it has drifted some predetermined distance from the desired position. It has also been. heretofore known to utilize a draw string hemmed into the edge of a filter screen and drawn over the end of the rollers to restrain the filter screen. While some of these previous methods have functioned reasonably well, they are characterized by mechanical complexity, being critical of adjustment and of considerableexpense to construct.

It is a primary object of the present invention to provide a means for tracking a limp endless filtering belt between two or more rollers which is simple and. economical to construct and reliable in operation.

Another object is to provide such a tracking means which does not require critical or frequent adjustment.

A still further object of the present invention is to provide a means for tracking a limp endless. filtering belt which in addition to the above will pull on the limp portion of the belt and thereby keep itlaterally taut.

The tracking device of the present invention is incorporated into one of the rollers which isencircled by the filter screen belt. The roller includes a center section of constant diameter, approximately the widthof the, limp portion of the belt, and a pair of end sections which are formed with a crown portion, the center of which is slightly greater than the diameter at each end of each end section. A flat, relatively narrow edging of rubber, leather or the like is fastened to both edges of the belt. Each edging, being of relatively rigid material, tracks and aligns itself on one of the roller crowns. By locating the crowns at a slightly wider spacing than the spacing of the belt edgings the belt will be kept laterally taut.

BRIEF DESCRIPTION OF THE DRAWING Other objects and features of the invention will become apparent to those skilled in the art as the disclosure is made in the following description of a preferred embodiment of the invention, as illustrated in the accompanying sheet of drawing, in which:

FIG. 1 is an elevational view of a portion of a filtering apparatus having an endless filter screen supported between a plurality of rollers, one of which incorporates the tracking device of the present invention;

FIG. 2 is a plan view of a portion of the apparatus in FIG. 1, showing the relationship between the filter screen and the tracking means associated with one of the rollers; and

FIG. 3 is a plan view of one end of the roller illustrated in FIG. 2', showing the relationship between the edge of the filter screen and the crown portion on the roller prior to the filter screen being pulled laterally taut in accordancewith the present invention.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1 an endless filter screen or belt 10 encircles atracking roller 12 and one or more additional rollers or drums 14 and 16, as required by the specific process employing the filter screen 10. Filter screen 10 may be fabricated from various foraminous materials. well known in the art; e.g., a woven synthetic fabric of either polyester or nylon. Such filter screens are traditionally very flexible and limp and do not yield to conventional belt tracking means used on more rigid belts.

The belt tracking means ofthe present invention concerns itself with the specific design and the relationship between the filter screen 10 and the tracking roller 12.

A flat, relatively narrow edging 20 is secured to both I edges of screen 10 so as to define a limp portion 18 therebetween. Edgings 20 are preferably made from rubber, leather or any other relatively rigid material.

Tracking roller 12 includes a center section 22 and a pair of end sections 24, as seen in FIG. 2. The center section 22 is of constant diameter and is approximately the same width as'the limp portion 18 of filter screen 10. The two end sections 24 are formed with crown portions 26 formed integral therewith. The diameter of the center of each portion 26 is slightly greater than the diameter at. the ends of each portion 26. The width of each end section 24 is approximately equal to width of the corresponding edging 20. The spacing of the crown portions 26 on roller 12 are slightly greater than the spacingof the edgings 20 on filter screen 10, as seen in FIG. 3, for reasons which will hereinafter become more apparent.

In operation, the filter screen 10 is positioned around plurality of rotating rollers l2, l4 and 16 to be driven therewith. Edgings 20, being of relatively rigid material, contact and align themselves on the rotating crown portions 26 of roller 12. Edgings 20 center themselves on the corresponding crown portion 26 and the limp portion 18, being attached thereto, is tracked and aligned therebetween. As the edgings 20 center themselves on the crown portions 26, the limp portion 18 is pulled and kept laterally taut because the crown portions 26 are spaced at a slightly wider distance than edgings 20.

The filter screen tracking mechanism of the present invention does not pull on or otherwise physically restrain the edge of the filter screen. it allows the filter screen to'track itself, with very little stress induced into the screening material. Further, the tracking mechanism as hereinabove disclosed retains the filter screen laterally taut without the use of additional mechanical devices.

It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that numerous modifications'or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.

What is claimed is:

1. In a filtering apparatus having an endless filtering belt supported between two or more rollers, said filtering belt having a relatively limp central section and a relatively rigid and substantially flat edging fastened to both edges thereof, at least one of said rollers including a central section having a constant diameter and a width substantially equal to the width of said belt central section and a pair of end sections, one at each end of said central section which are formed with crown portions having a diameter which is greater than the diameter of said central section, each of said edgings being positioned so as to track and align themselves on a corresponding crown portion.

2. The invention as defined in claim 1 whereinsaid crown portionsare spaced a slightly larger distance apart than the spacing of a central portion of each of said belt edgings so as to cause said central section of said belt to remain laterally taut as said edgings center themselves on said crown portions.

3. The invention as defined in claim 2 wherein said edgings are made from a rubber material.

4. The invention as defined in claim 2 wherein said edgings are made from a leather material.

5. The invention as defined in claim 2 wherein said filtering belt is made from a filtering cloth.

6. The invention as defined in claim 2 wherein the of said end sections. 

1. In a filtering apparatus having an endless filtering belt supported between two or more rollers, said filtering belt having a relatively limp central section and a relatively rigid and substantially flat edging fastened to both edges thereof, at least one of said rollers including a central section having a constant diameter and a width substantially equal to the width of said belt central section and a pair of end sections, one at each end of said central section which are formed with crown portions having a diameter which is greater than the diameter of said central section, each of said edgings being positioned so as to track and align themselves on a corresponding crown portion.
 2. The invention as defined in claim 1 wherein said crown portions are spaced a slightly larger distance apart than the spacing of a central portion of each of said belt edgings so as to cause said central section of said belt to remain laterally taut as said edgings center themselves on said crown portions.
 3. The invention as defined in claim 2 wherein said edgings are made from a rubber material.
 4. The invention as defined in claim 2 wherein said edgings are made from a leather material.
 5. The invention as defined in claim 2 wherein said filtering belt is made from a filtering cloth.
 6. The invention as defined in claim 2 wherein the width of said edgings is substantially equal to the width of said end sections. 